[PATCH 2/7] vfs: O_NONBLOCK|O_CREAT open shouldn't wait for directory delegation

[NeilBrown <neilb@ownmail.net>]

From: NeilBrown <neil@brown.name>

An open() of a regular file can block if there is an active lease on that
file, but this can be prevented by opening with O_NONBLOCK.
An open(O_CREAT) of a non-existent file can block if there is an active
delegation on the parent directory but this CANNOT be prevented with
O_NONBLOCK.

If nfsd is to use common VFS code for open/create it needs to be able to
prevent this blocking.  It is conceivable that a user-space application
might need this too.

So extend O_NONBLOCK protection to not block on a directory delegation
when creating a file.

Fixes: 134796f43a5e ("vfs: break parent dir delegations in open(..., O_CREAT) codepath")
Signed-off-by: NeilBrown <neil@brown.name>
---
 fs/namei.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index c9ac703110f8..c4be59213352 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4554,7 +4554,12 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
 		goto out_dput;
 	}
 
-	error = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE, &delegated_inode);
+	if (op->open_flag & O_NONBLOCK)
+		error = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE,
+					NULL);
+	else
+		error = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE,
+					&delegated_inode);
 	if (error)
 		goto out_dput;
 
-- 
2.50.0.107.gf914562f5916.dirty